Method of cracking hydrocarbons



Oct. l0, 1950 J. H. sHAPLl-:IGH

mamon oF cRAcKING HYnRocmoNs Filed Aug. 22, 1946 /3-9 Mme-f? o y f m fmm a n f MM W mw mm r 0 im T M s ,f w. Nspr w .E M vH @as e .am N G M 6kr f m fr m J Y M P 2 R M f 0 W OIL Patented Oct. 10, 1950 2,525,276 vMETHOD F oRAcKrNG HYDRooARBoNs James H. Shapleigh, Wilmington, Del.,assignor to Hercules Powder Company, Wilmington, Del., a corporation ofDelaware Application August 22, 1946, Serial No. 692,345

This invention relates to the cracking of hydrocarbons and moreparticularly to a novel process and apparatus for the thermal crackingof normally liquid, as well as normally gaseous, hydrocarbons.

In the art of cracking hydrocarbons with one objective the substantialproduction of olenes. the fear of serious carbon deposition togetherwith a fear of ethylene polymerization, has resulted in a retardation ofimprovement whereby the state of the art is substantially behind thesomewhat related art of cracking hydrocarbons for hydrogen production.The processes for ethylene production are actuallypointed toward use ofonly the most highly favorable raw materials, usually propane, keroseneand gas oil or at the' most, steam distillates from heavier oils.Processes using whole oils are singularly lacking and the facilities ofreaction control existing in the art of hydrogen production are absentin the majority of processes for ethylene production, due probably tothe assumption, perhaps unwarranted, that ethylene is more difficult toproduce.

The art is therefore in need of a practical ilexible tive processes arethose of Nagel (U. S.- Patent No. 2,111,899) and Grebe (U. S. Patent No.2,176,962) who use the principle of ilash mixing and reacting separatestreams of hydrocarbon and steam highly preheated so as to beself-sufcient as to total heat requirement. Another representativeprocess for the production of ethylene is carried out in a refractoryregenerative type of apparatus such as shown, for example, in U. S.Patent No. 2,208,123 to Duncan.

In contrast to the iiash heat method of Nagel and Grebe or theregenerative type of Duncan are the tubular-type processes in whicholenes are produced from sulfur-containing hydrocarbons and steam inchrome-nickel alloy tubes under controlled temperature conditions. Thepatents to Wietzel (1,934,836) and Balear (2,218,495) and Reissue PatentNo. 21,521 to J. H. Shapleigh disclose representative processes of thistype. Wietzel discloses the use of chrome-nickel alloy in the catalyticcracking of hydrocarbons With 13 claims. (ci. 19t-s3) steam in an artutilizing sulfur-containing gases within the limits allowed by catalystsin use. Shapleigh discloses a process for treating fluid reactants in atubular furnace fired at a plurality of spaced points to producecountercurrent firing and flexible temperature control of the reactingfluids. Balcar discloses a way of preparing a steam distillate, butfails to describe all important details of how to furnace process toavoid carbon deposition or to control reaction.

The tubular-tyle process has been highly def' veloped in the eldparticularly applied to hydrogen, and it is known to the few skilled inits use how successful it is in controlling temperature of the reactingiluids. Even so, it is recognized that in treating hydrocarbons,particularly in preheating them in the temperature zone a few hundreddegrees short of that necessary for a good reaction velocity, there is agreat tendency for carbon deposition to take place, the seriousnessdepending upon the feed stock used. It is also possible to prolongcontact of hydrocarbons with excessively heated surfaces to thedetriment of economic oil cracking, if operated by unskilled hands. Thislack of familiarity with tubular furnace operation has contributed muchto a fear of carbon deposition, excess cracking, polymerization andgeneral mechanical difliculty such as short tube life. It may accountfor the less flexible flash heat-type process.

Now in accordance with the present invention it has been discovered thatif atomized oil or oil vapor mixtures at noncondensing temperatures andat substantially atmospheric pressure, are injected suddenly into astream of steam within an externally heated alloy tube, the mixture canbe supplied with heat during its further passage through the remainderof the tube to bring about satisfactory cracking of oils with a minimumof carbon deposition and a maximum of flexibility of temperature, timeand pressure control. The

process of this invention provides an improve-I ment not only in oleneproduction but in the cracking of oils and gaseous hydrocarbons toproduce maximum value of total products, and in selective production ofparticular products. Whole oils, i. e., those containing asphalt and theheavy hydrocarbons, as well as the lighter hydrocarbons and the normallygaseous hydrocarbons, may be used without substantial carbon deposition.In fact, no serious carbon deposition whatsoever has been found to occurWithin the cracking tube in commercial size application. Thisconstitutes an established successful improvement not heretoforepossible without the hazards of carbon build-up.

In practice hydrocarbons, such as liquid petroleum hydrocarbonsincluding deasphalted oils and crude stocks, for example East Texascrudes, are atomized with steam (or other suitable gas) Without heatingto a thermal decomposition temperature, and then injected in a novelmanner into a stream of superheated steam (or other suitable gaseousmedium containing the required amount of sensible heat) at one end of anexternally heated alloy tube to substantially completely vaporize theoil and form a gaseous mixture of hydrocarbons and steam and immediatelythereafter passing the mixture through the remainder of the tube whichis maintained at the desired temperature by direct heating. 'I'hehydrocarbons are thereby cracked into a mixture of constituentsincluding olenes, which may then be treated in any suitable manner toretard polymerization, to separate normally liquid from the normallygaseous components and/or to separate liquid and/ or gaseous streamsinto components. The process is continuous and results in a product highin olefine content.

Having now indicated in general the nature and purpose of the presentinvention, there follows a more detailed description of the inventionwith reference to the accompanying drawing in which Figure 1 represents,diagrammatically, a

ow sheet indicating the production of olenes and other products by thethermal cracking of a petroleum oil in the presence of steam, and Figure2 is a, modification of the novel injection and mixing means of thisinvention.

Referring now to Figure 1 of the drawing the petroleum oil is deliveredby means of a pump I' from any suitable oil reservoir to a preheater 2where it may be heated with steam by indirect heat exchange to apredetermined temperature depending upon the raw material used. 'Ihepreheated oil is passed through a measuring valve 3, and delivered to amixer 4 where it is atomized and partially vaporized with a primarystream of saturated or superheated steam (called primary steam) which isdelivered to the mixer through a measuring valve 5. The atomized andpartially Vvaporized mixture of oil and primary steam is then injectedinto a concurrently moving, concentrically disposed, body of a secondarystream of steam (called secondary steam) by means of an injection tube6. The injection tube 6 extends a predetermined distance into theentrance end of a reaction tube l, heated externally by a, furnace I0,and is provided with a rounded end 8having perforations 9. AThe atomizedand partially vaporized mixture of oil and primary steam is confinedwithin the injection tube until it reaches the exit end 8 thereof whenit passes through the perforations 9 in a plurality of streams. Thus, itis heated to a predetermined temperature by indirect heat transfer fromthe furnace.

The secondary steam is delivered to the reaction tube 'I by means of aconduit II controlled by a measuring valve I2. It flows concurrently,but out of direct contact, with the oil-primary steam mixture, theatomized oil-primary steam mixture being within, and the secondary steambeing outside of, the injection tube. I'he oilprimary steam mixtureexits from the injection tube through the perforations 9 and into theannular stream of secondary steam. By this procedure, the atomizedoil-primary steam mixture is intimately and quickly admixed with thesecondary steam, and quickly heated by direct heat exchange of sensibleheat of the secondary steam, which has been heated in the upper portionof the reaction tube.

The atomized and previously partially vaporized oil is further vaporizedand the intimate gaseous admixture of hydrocarbons and steam is passedquickly through the indirectly heated, annular, reaction space betweenthe walls of the reaction tube and a tubular space reducer I3 disposedaxially within the reaction tube.

vThe tubular space reducer I3 is provided at its upper end with aclosure I4 and at its lower end with a perforated plate I5. Steam may beintroduced to the space reducer I3 by a pipe I6 controlled by a valveI'I. In operation a small amount of steam is admitted to the spacereducer I3 to maintain complete displacement of any hydrocarbons whichwould otherwise enter the interior thereof through the perforated plateI5. Regulation of the steam passing into the member I3 additionally aidsin controlling the temperature of the steam-hydrocarbon mixture passingthrough the reaction tube.

The reaction product containing olenesis withdrawn" from the reactiontube through a conduit I4, quenched by liquid hydrocarbons and themixture passed toa plate column for separation and recovery of fthenormally gaseous and normally liquid products. Quenching, separation andrecovery of products may be accomplished by means well known in the art.Products from the plate column may then be disposed of as such or mixedwith feed stock or otherwise recycled through the process.

In the modification of the device shown in Figure 2 a, portion of theinjection tube 6 is surrounded by a concentric tube or jacket I8 havingits upper end open as at I9. The space between the reaction tube 'I andthe tube or jacket IB is lled with ring packings or other suitablematerial 20 to promote heat transfer to the secondary steam and/or toreduce the radiation of heat to the injection tube The packing material20 is suitably supported on a perforated plate or screen 2| mountedadjacent the exit end of the injection tube. Steam pipes 22 and 23 areconnected to a steam header 24 and serve to introduce the secondarysuperheated steam to the lower portion of the tube I8 and to the upperportion of the reaction tube 1, respectively. Suitable measuring valves25 and 26 selectively control the flow of steam through the pipes 22 and23.

In the operation of this form of the device all or a portion of thesecondary steam may be introduced into the lower portion of the tube orjacket I8 and passed countercurrent to the ilow within the injectiontube prior to entering the outer concentric sxpace. Steam passingthrough the tube I8 exits therefrom through the open end I9 and mixeswith any secondary steam introduced through the pipe 23. The mixturethen passes downwardly through the packing material 20 and mixes withthe hydrocarbon-steam mixture as it exits from the injection tube. Thisarrangement provides a very eective temperature control of thesteam-hydrocarbon mixture flowing through the injection tube while atthe same time permitting the secondary steam passtube the more B. t. u.input to the primary steam is required. This is favored by oil preheat,by the use of superheated steam and by injection tube conditionsconducive to high heat tranfersuch as high velocity, use of hns, etc.,for increasing surface and turbulence. The steam-oil ratio can also bevaried to assist attainment of the best conditions. The exact conditionsof temperature of oil and steam, manner of mixing and ratio in whichthey are mixed in order to obtain an atomized and partially vaporizedoil-primary steam mixture, will depend upon the characteristics of thegiven hydrocarbon and the conditions of treatment as will be understoodin the art.

The atomized and partially lvaporized mixture of hydrocarbon and primarysteam is then passed through the heated by the superheated steam flowingon the exterior of the tube and by indirect heat from the wall of thereaction tube. The temperature of the mixture as it exits from theinjection tube may vary from about 250 F. to about 800 F. but preferablydoes not exceed about 600 to 650 F. The temperature selected dependsupon the volatility of the hydrocarbon, its stability to heat, the ratioof hydrocarbon to steam and the time in transit. A temperature isselected which results in partial vaporization of the hydrocarbon by thetime it leaves the injection tube but which does not result insubstantial thermal decomposition of the hydrocarbon constituents withinthe injection tube. It will be understood that the hydrocarbons of thepetroleum fractions with a low boiling range are more easilyvolatilizedmore stable at elebut, at the same time, are

those with a higher vated temperature than are boiling range.

rlhe heated mixture of oil and primary steam, in which the oil has beenpartially vaporized, is then injected into a. concurrently moving,superheated body of secondary steam confined within the reaction tube.The objective, at this point, is to flash heat and mix the hydrocarbonvapor and particles by quickly injecting the hydrocarbon into the hotsecondary steam with minimum or no impingement on the high temperaturecracking tube wall which, in this zone, is at a temperature of about1500 to 1900 F. The stream of secondary steam acts to cushion theprojected vapors and particles and to turn the hydrocarbon trajectoriesinto axially promoted, turbulent flow into a zone at reactiontemperature. In this manner, the vaporization of the oil is quicklycompleted, while at the same time, the hydrocarbons are flash heated tosubstantially reaction temperature and the mixture supplied withreaction heat from the furnace along its reaction path. These conditionsminimize the carbonproducing type of thermal decomposition of thehydrocarbons and are conducive to elimination f any carbon formed.

There is considerable latitude as to the method of injecting the primarysteam-hydrocarbon mixture into the stream of secondary steam. Themixture may be injected at any angle to the secondary stream. It may beinjected -at multiple points laterally and/or axially. It may beinjected tangentially or by any other means suitable to the objective.Angular injection at about 60 away from the axis with a small amount at0 along the axis and from a conical or spherical end, is preferred.

The position of the along the Icracking tube can injection point axiallybe varied. For instance, with a heavy oil it is preferred to utilize apoint about 6 feet from the furnace arch, wall or hearth nearest the gasentrance end of the furnace. However,v for an oil of Diesel grade, goodresults are obtained, utilizing about 3 feet.

The injection tube may be jacketed or unjacketed depending upon otherfactors. For example, when packing is not used in the secondaryinjection tube where it is steamspace, it may be desirable to reduce theradiation effect between the cracking tube and the injection tube wallsto promote control of injection temperature. This can be done by use ofa jacket on the injection tube and with all or a part of the secondarysteam passed through the jacket countercurrently to the primarysteam-hydrocarbon mixture flow and subsequently into the secondary steamchannel. In other cases it may be desirable to utilize both the jacketand packing material as shown in Figure 2 of the drawing.

The secondary steam is supplied to the reaction tube in the manner shownin either Figure 1 or Figure 2, one objective being to prepare asecondary stream of steam at temperatures preferably ranging from about1000 F. to about 1600" F. at the point of mixing with the primarysteamhydrocarbon mixture exiting from the injection tube. Thetemperature to be attained in any particular case depends upon therelative amounts of secondary steam and oil-primary steam mixture, thetemperature of the oilprimary steam mixture just prior to mixing withthe secondary steam, the thermal stability of the hydrocarbons, and thelike. The above objective may be-realized by utilizing superheated steamand by further heating the steam as it passes through the reaction tube.Various methods may be used, if desired, to promote and/or accelerateheat transfer from the reaction or cracking tube. One method involvesthe use within the cracking tube of surface exposed to radiant heat.Another method involves the use of heat-resistant metallic packingsupported on a perforated plate attached to the injection tube as shownin Figure 2. If desired the packing may be confined within a containingmetal tube concentric with the cracking tube and suitably suspended froman end plate of the same or otherwise mounted on the injection tubeand/or perforated plate to form a removable packing assembly.

On mixing of the oil-primary steam and the secondary steam a flashlowering of hydrocarbon partial pressure takes place simultaneously withflash heating an-d with further heating from the Wall of the crackingtube, and soon thereafter from the wall of the inner spacer tube. Thecombination of low partial pressure and temperature immediately orquickly thereafter creates a condition whereunder all hydrocarbonsexcept extremely small amounts of high boilers must be in the vaporstate and undergoing reaction. The higher the temperature 'at the timeof mixing the oil-primary steam and the secondary steam, the morecomplete the hydrocarbon vaporization on flash mixing.

The most satisfactory conditions as to temperatures, ratio of primarysteam to oil, ratio of secondary to primary steam, etc., will bedetermined by experiment for each particular oil or set of otherconditions such as feed rate, type of oil, etc.

The total amount of steam used, primary plus secondary, will depend upona number of considerations. Since in the process of this invention thesteam serves essentially as a bulk heat meing through the packingmaterial to be quickly heated to the desired degree.

In accordance with this invention and to illustrate in more particularthe method of prod/poing oleiines and other products by thethermal/cracking of hydrocarbons in the presence of steam, severalexamples in tabular form are given below. These examples illustratetheresults obtained from the use of various type oils when feeding each oilin its entirety, i. e., without any prior separation of favorable fromunfavorable components, to the cracking tube. Asphalt and all componentsof each oil entered the cracking tube.

TABLE' to obtain maximum values for industrial use and particularly foruse in the chemical industry.

The successful cracking oi' hydrocarbonswith attendant production ofolenes and other prod- 5 ucts by the thermal cracking of hydrocarbons ina tubular cracking furnace in the presence of steam primarily depends(1) on the proper preparation and introduction of the steam-hydrocarbonmixture into the alloy cracking tube and 0 (2) passing the mixturethrough the remainder of Results of tests on various oils E. Texas #2Fuel Deasphaifed Residual Crude (a) (b) (a) (ll) (c) (b) Cu. Ft. ExitGas per 100 lbs. Oil Cracked. S. T. P. and

Dry Basis 1, 82o 1, 965 1,395 1, 500 1,785 1, 53o 2,240 Per CentOleilnes 46. 3 7 61. 7 57. 4 46. 0 53. 3 41. 0 Steam-Oil Wt. Ratio:

Primary 1.0 .9 .6` .6 .6 .9 .9 Secondary .9 1.0 2.0 1.4 1.9 2.0 2. 1Total 1.9 1.9 2. 0 2. 0 2. 5 2. 9 3. 0 Temperatures F.:

Injection Tube Exit--- degrees.- 255 260 260 300 300 290 310 ec Steam atInj. Pt.. .do- 1,150 1,090 1, 270 1,285 1,310 1,310 1,380 Avg.Tube-Metal Wall. do. l, 650 1, 650 1, 585 1, 610 1,640 1,600 1,650 Lbs.Oil Feed Per Tube/Hr 124 155 146 154 154 102 102 T Imm-firm Angularnetrarion of secondary steam Per Cent Feed Cracked 54 I 48 re 47 49 51 I64 I 73 The foregoing examples do not represent maximums nor optimums.The process is flexible whereby feed rates can be substantiallyincreased, the percent oil cracked varied up or down, and the gasproduced per 100 pounds of oil increased or decreased. Gas rates of 3940cubic feet per` 100 pounds of oil have been obtained containing 18%olenes with a good percentage of C2H2, and 3690 cubic feet with 20% C2H2plus 02H4. This represents a rate of gas production of the order of12,000 cubic feet per barrel. The iigures in the table above represent arate of gas production of the order of 4000 to 7500 cubic feet perbarrel of oil fed.

Likewise it has been found that some oils can beneeially be crackedsubstantially 100%, obtaining, for example, 30% or better total'olenesand eliminating the step of fractionation separation of gas fromuncracked oil. Thus, for instance, the product from the reaction columncan be quenched with intermediate hydrocarbon fractions, or with water,and the gas passed direct to pressure-low temperatureabsorption-liquifaction equipment or to adsorption processes for gascomponent separation.

Depending upon the oil cracked and upon the precise process conditionsused, there is obtained, under conditions of partial cracking and afterquenching and condensation, a liquid product which may be lighter thanwater, whereas under other conditions the unfractionated condensate maybe a creamy liquid heavier than water. The components of the uncrackedoil vary but conditions under which the cracking takes ,place ailect thepercentage of any group of components and of any one in particular.

The liquid portion may contain for instance, butadiene, isoprene,styrene, indene, naphthalene and resins aside from more normallyexpected cuts. This invention, therefore, comprises not only anadvantageous `process for economically producing oleilnes but a processfor cracking oils 35 introducing the steam-hydrocarbon mixture accordingtothe present invention consists in atomizing and partially vaporizingthe hydrocarbon preferably with steam, passing the atomized andvpartially vaporized mixture of hydrocarbon and lsteam through aninjection nozzle extending into the cracking tube and quickly injectingthe atomized and partially vaporized mixture into a stream ofsuperheated steam. Optional preheat- 'ing of hydrocarbons isaccomplished by any suitable type of device such as an indirect heatexchanger, the degree of desired heat varying with the type of rawmaterial and being supplied in insuiicient amount to cause anyappreciable decomposition of the hydrocarbon. Desirable hydrocarbonpreheat temperatures at this point are in the order of about 250 F. butmay be varied from about 200 F. to about 500 F. under difierentoperating conditions and when treating diiferent kinds of hydrocarbons.No preheat need be used with light hydrocarbons or gaseous hydro- 5carbons and dependence is placed on the heat in the secondary steam plusindirect heat to the injection tube.

The hydrocarbon, when in liquid form, is atomized and partiallyvaporized with high pressure primary steam, the objective being to putthe hydrocarbon into either the vapor state or a fine state ofsubdivision. Hydrocarbons readily volatilized, such as ethane andpropane. can be fed to the injection tube wholly in the vapor state.With oils the primary steam functions to prepare the oil in a line stateof subdivision by means of a mixer or atomizer, to retard coalescenceprior to injection into the secondary steam and to promote partialvaporization. Tthe lowering of the partial pressure of the oil by thesteam within the injection tube lowers the boiling point and assistsvaporization. To the extent that vaporization can occur without carbondeposition, it is favorable to the process.

The higher the vaporization in the injection No. 21,521 to James H.Shapleigh which may be modiiled in this process to either countercurrentor parallel flow of process and combustion gases.

The reaction tube of the present invention preferably consists of aninner spacer tube and an outer cracking tube concentrically arranged, asshown in Figure 1, and made from a chrome-steel alloy containing about25% chromium, 20%

nickel, 1% columbium and the remainder substantially iron. Thesespecific proportions are merely given for purposes of illustration,however, and it will be realized that other suitable alloys may be used.The reaction tube may be vertical, horizontal or inclined depending onthe conditions of use. space available, etc. Very effective temperaturecontrol is afforded by direct heat applied to the exterior of the outertube in the manner heretofore stated, and by the added surface providedby the spacer tube.

If desired, the inner spacer tube may be replaced by packing rings orother suitable material or the spacer tube removed and the emptyreaction tube utilized. However, in each case, conditions must .be suchas to give the required heat transfer and time of passage within thereaction zone.

The steam-hydrocarbon mixture may be injected into the reaction tube ateither end, i. e., at the end from which combustion gases exit or at theopposite end. As applied to Figure 1, for example, injection may takeplace either near the top of the tube as shown, or near the bottom ofthe tube, combustiongases flowing countercurrent or parallel to thesteam-hydrocarbon mixture, and being discharged adjacent either end ofthe tube as desired.

Although it is desirable in most instances to obtain a high percentageof cracking of the hydrocarbons it is possible and sometimes desirableto obtain a partial cracking, i. e., from about 50% to 75% cracking, andto recycle portions of' the uncracked products for mixture with feedstock, thus resulting in a favorable lower viscosity net feed. A furtheradvantage of this procedure lies in the effective use of recycle stocksfor quenching the reaction products from the cracking tube.

The present process is advantageously carried out at substantiallyatmospheric pressure although pressures somewhat above or belowatmospheric can be used with satisfactory results. In addition, pressureof to 100 pounds per square inch can be used successfully to regulatetypes and proportions of products obtained. Operating pressures of thisorder may be obtained by providing a regulating valve at the end of thecracking system.

By the process of injecting and flash heating, in accordance with thisinvention, it will be noted that the liquid hydrocarbons containingsulfur do not come in contact with the metal wall in any case exceptpossibly with traces of very high boilers and then not to anyappreciable or serious extent. The hydrocarbons within the cracking tubeproper, are above the dew-point. Further, the sulfur containinghydrocarbon vapors are out of contact with the metal wall at thetemperatures whereunder carbide precipitation and any ,coincident sulfurattack normally occurs to any serious extent. Under the conditions ofinjection the mercaptans present are converted to H25 and cause nodifficulty under the temperature and hydrocarbon dew-points prevailing.

The process of this invention is adaptable to the injection ofemulsions, oils containing catalysts, and oils containing anti-carbonforming materials. It is applicable to the treatment of normally gaseousas well as normally liquid hydrocarbons. Although preferred apparatusand procedure have been set forth, it will -be realized that manychanges may be made without departing from the scope of the invention.

A particular advantage of the present invention resides in the fact thathigher yields of olenes and valuable liquid products are obtained withless carbon trouble than has hitherto been possible in the cracking ofhydrocarbons in tubular furnaces. A further advantage resides in thesuccessful and economical treatment of whole oils, the heavier liquidpetroleum hydrocarbons, deasphalted oils and crude stocks containingasphalt. This makes it possible to take advantage of the availabilityand economy of such raw materials and without limitation on thegeographical location of plants hitherto considered necessary.

This application is a continuation-in-part of my copending applicationfor United States Letters Patent, Serial No. 576,481, filed February 6,1945.

The words "concurrent and parallel, as used in the specification andclaims, apply to the flow of fluids and mean parallel flow in the samedirection as contrasted to countercurrent, meaning parallel flow inopposite directions.

What I claim and desire to protect by Letters Patent is:

1. A process of cracking hydrocarbons which comprises flowing afinely-diffused hydrocarbon along an inner path in a cracking tube,flowing steam concurrent therewith along an outer path concentric withthe inner path and in contact with the cracking tube, applying heatktothe cracking tube to superheat the steam, causing the hydrocarbonflowing from the inner path to mix directly with the steam flowing alongthe outer path in contact with the cracking tube, and immediatelypassing the mixture of steam and hydrocarbon through the cracking tubewhile applying heat to bring about satisfactory cracking of thehydrocarbon without appreciable carbon deposition.

2. A process of cracking hydrocarbons which comprises flowing afinely-diffused hydrocarbon along an inner path in a cracking tube,flowing steam concurrent therewith along an outer path concentric withthe inner path and in contact with the cracking tube, applying heat tothe cracking tube to superheat the steam to a temperature above about1000 F., causing the hydrocarbon flowing from the inner path to mixdirectly with the steam flowing along the outer path in contact with thecracking tube at a temperature above about 800 F., and immediatelypassing the mixture of steam and hydrocarbon through the cracking tubewhile applying heat to bring about satisfactory cracking of thehydrocarbon without appreciable carbon deposition.

dium, a partial pressure reducer for hydrocarbons and as an. anticarbondeposit material, it can be varied in relation to the quantity of oilfed to vary conditions of time of contact or temperature. to regulatetemperature conditions of injection, and temperature gradients along thereaction path both radially and axially. 'Ihe steamhydrocarbon ratio canbe varied to give either high or low ratios as desired i'or less dilcultor more diicult feed stocks. but normally will be in the range of ratioof .1 to 1 to 5 to 1. It is preferred to use steam-hydrocarbon ratiosvarying fromabout1to1to3to1.

The exact manner in which the steam is pro-` portioned between primaryand secondary depends upon a number of factors as already indicated. Insome cases it may be desirable to atomize the hydrocarbon with someother medium than steam, such as for example hydrogen, nitrogen,combustion gases, etc., under pressure. In such cases all of the steamis furnished as secondary steam. On the other hand, all of the steam maybe introduced in the atomization, and some other heated gaseous mediumbesides steam may be used for the heating and diluting in the secondarystream of gas. Hot combustion gases, heated hydrogen or nitrogen, etc.,may be used.

An important part of the present invention and one which aids greatly inattaining the objective of eillciently cracking hydrocarbons in thepresence of steam is the formation of an atomized and/or vaporizedmixture of the higher hydrocarbons with steam, maintaining the materialin a state such that there is minimum coalescence of the hydrocarbons,and flash heating the mixture to a cracking temperature withoutappreciable carbon deposition.

Although it is `preferred to form the desired mixture of steam andvaporized hydrocarbons within the cracking tube, as Aillustrated anddescribed, it may under some circumstances be desirable and satisfactoryto form the mixture separately and then pass it to and through thereaction tube. This may be accomplished-by providing a separateinjection and mixing means. embodying the principles already described,and connecting it to-the reaction tube by a flanged coupling, pipe orother suitable connecting means.

The thing of importance is to obtain a gaseous mixture comprising steamand vaporized hydrocarbons from higher petroleum hydrocarbons,particularly normally liquid petroleum oils, containing about .1 to 5parts by weight of steam for each part by weight of oil. at atemperature of from about 1000 F. to about 1600 F., substantially freeof free carbon.

The gaseous mixture of steam and vaporized hydrocarbons which should beat a temperature of at least about 700 F. and preferably from about 1000F. to about 1600 F. is immediately passed through the remainder of thecracking tube. Factors which are of primary importance in this phase ofthe process are temperature of the steam-hydrocarbon gas, metal walltemperature in its relation to temperature gradient, and contact orreaction time. These factors depend on the characteristics of the.hydrocarbon being cracked, the ratio of quantity of oil to quantity ofsteam and/or other gas, percentage cracking desired, etc. In general,steam-hydrocarbon temperatures varying from about 1100 F. to about 1700F, give the gest results and are preferred. Such temperatures are not,however, critical and may be extended to provide conditions mostfavorable to the specic oil and products sought.

10 1 Metal wall temperatures areregulated in relation to theother-conditions of treatment to give the desired temperature andtemperature gradient within the reaction zone.

Reaction time under given conditions of treatment will depend on theselected temperature and hydrocarbon partial pressure. When thetemperature is increased the reaction time will be correspondinglydecreased and vice versa. Generally it has been found that comparativelyshort reaction times varying from-about .l to 5 seconds and preferablyfrom about .1 to 1 second are most effective.

Reaction products from the cracking tube are preferably quenched by theuse of liquid hydrocarbons and the quenched gas stream passed to afractionating tower system' to separate the normally liquid and gaseousproducts.

The flexibility of the process of the present invention is partlyobtained through the ability to control temperature gradients andtemperature itself both axially and radially in the cracking tube.

Radially it is obtained with respect to a point or zone on the tube wallby firing the furnace to give a specific tube wall temperature, and bycontrolling the transfer of heat to the gas stream, for example, bychanging the gas velocity, by changingihe area for gas passage or byincreasing the throughput, by 4changing the ratio of outer,

and inner tube surface, by the use of fins, deflectors, etc., toincrease turbulence, by changing the steam-oil ratio or the diluent-oilratio generally, and by the use of packing material.

Axially, control may be obtained in a number of ways. One procedureinvolves the use of a furnace in which heat is selectively applied atspaced points along the periphery of the reaction tube, the hotcombustion gases flowing upwardly along the tube countercurrent to thenow of steam-hydrocarbon mixture therethrough, and passing oi through aue exit adjacent the end at which the steam hydrocarbon mixture isinjected into the secondary steam. By this procedure furnace zonetemperatures can be adjusted at will, but a high downward gradient, i.e., high temperature at the injection zone and low temperature at thegas exit becomes increasingly dimcult to obtain, the greater the desiredgradient.

In a slightly different procedure hot combustion gases are passeddownwardly around the reaction tube, parallel to and concurrent with theflow of steam-hydrocarbon mixture therethrough, and are dischargedthrough a flue exit adjacent the end of the tube opposite that in whichthe steam-hydrocarbon mixture is mixed with the secondary steam, heatbeing applied at spaced points along the tube as before. This proceduregives good control, particularly where high temperature is required inthe injection zone and low temperature is required in the reaction zone.Either of the above procedures may be modified by firing adjacent theend of the tube rather than at spaced points along the tube.

In a still different procedure cross radiation can be materiallylessened and full benefit from a selected firing plan realized whenutilizing a single chamber furnace. In this case, by the use of one ormore partition walls along the axis of the tube, zones are formed whichcontribute to finer points of gradient control. Tubes and com- .bustionproducts pass through said partition walls by means of proper openings.

These procedures may be carried out in either i3 3. A process ofcracking hydrocarbons which comprises owing a finely-diffusedhydrocarbon containing more than two carbon atoms per molecule andheated to a temperature below' about 800 F. along an inner path in acrackingv tube, owing steam concurrent therewith along an outer pathconcentric with the inner path and in contact with the cracking tube,applying heat to the cracking tube to superheat the steam to atemperature above about 1000 F., causing the hydrocarbon flowing fromthe inner path to mix directly with the gaseous medium flowing along theouter path in contact with the cracking tube at Ia temperature aboveabout 800 F., and immediately passing the mixture of steam andhydrocarbon through the cracking tube while applying heat to bring aboutsatisfactory cracking of the hydrocarbon without appreciable carbondeposition.

4. A process of cracking hydrocarbons which comprises flowing a gaseoushydrocarbon along an inner path in a cracking tube, flowing gaseousmedium concurrent therewith along an outer path concentric with theinner path and in contact with the cracking tube, applying heat to thecracking tube to superheat the gaseous medium, causing the hydrocarbonflowing from the inner path to mix directly with the gaseous mediumflowing along the outer path in contact with the cracking tube, andimmediately passing the mixture of gaseous medium and hydrocarbonthrough the tube while applying heat to bring about satisfactorycracking of the hydrocarbon without appreciable carbon deposition.

5. A process of cracking hydrocarbons which comprises flowing gaseoushydrocarbon along an inner path in a cracking tube, flowing gaseousmedium concurrent therewith along an outer path in the cracking tube andin contact with the cracking tube wall, applying heat to the crackingtube, causing the hydrocarbon flowing from the inner path to mixdirectly with the gaseous medium flowing along the outer path in contactwith `tl1c cracking tube, and immediately passing the mixture of gaseousmedium and hydrocarbon through the tube while applying heat to bringabout satisfactory cracking of the hydrocarbon without appreciablecarbon deposition.

6. A process of cracking hydrocarbons which comprises flowingfinely-diffused hydrocarbon along an inner path in a cracking tube,flowing gaseous medium concurrent therewith along an outer path in thecracking tube and in contact with the cracking tube Wall, applying heatto the cracking tube, causing the hydrocarbon flowing from the innerpath to mix directly with the gaseous medium flowing along the outerpath in contact with the cracking tube, and immediately passing themixture of gaseous medium and hydrocarbon through the tube whileapplying heat to bring about satisfactory cracking of the hydrocarbonwithout appreciable carbon deposition.

7. A process of cracking hydrocarbons which comprises flowing a nelydiffused hydrocarbon along one path, flowing steam-'countercurrentthereto along a second path concentric therewith, flowing the same steamalong a third path concentric with and countercurrent to the flow oi'steam in the second path, applying indirect heat to the third path tosuperheat the steam, causing the finely diffused hydrocarbon to mix withthe steam flowing through the third path, and immediately passing themixture of steam and hydrocarbon through a cracking tube while supplyingheat thereto to bring about satisfactory 4 cracking of the hydrocarbonwithout appreciable carbon deposition.

8. A process of cracking hydrocarbons which comprises flowing a finelydiffused hydrocarbon along one path, flowing steam countercurrentthereto along a second path concentric therewith, admlxing additionalsteam with the steam ilowing from the second path., flowing theresulting steam mixture along a third path concentric with andcountercurrent to the flow of steam in the second path, applyingindirect heat to the third path to superheat the steam, causing theflnely diiused hydrocarbon to mix with the steam' flowing through thethird path, and immediately passing the mixture of steam and hydrocarbonthrough'a cracking tube while supplying heat thereto to bring aboutsatisfactory cracking of the hydrocarbon without appreciable carbondeposition.

9. In a device for the cracking of hydrocarbons inv a furnace theimprovement comprising a cracking tube, spacer means inthe cracking tubeforming-an annular passage, injector means extending intothe crackingtube, means for flowing gaseous medium along the injector meansexteriorly thereof, means for heating the gaseous medium as it flowsalong the injector means, and means for passing a partially vaporizedhydrocarbon through the injector means and injecting it into the ilow ofgaseous medium to form` a mixture of hydrocarbon 'and gaseous medium.

10. In a device for the cracking of hydrocarbons in a furnace, theimprovement comprising an exteriorly-heated cracking tube, spacer meansin the cracking tube forming an annular passage, injector meansextending into the cracking tube, means for owing gaseous medium alongthe injector means exteriorly thereof and in contact with the crackingtube, means for passing a gaseous hydrocarbon through the injector meansand injectingit into the ilow of gaseous medium to form a mixture ofhydrocarbon and gaseous medium, and means for passing gaseous mediumthrough the spacer means.

11. In a device for the cracking of hydrocarbons in a furnace theimprovement comprising injector means, means for passing a nely diffusedhydrocarbon through the injector means, means for flowing steam througha confined path concentric with the injector means, means for flowingthe same steam through a second confined path concentric with therst-mentioned path, the flow of steam in the first path beingcountercurrent to and the flow of steamin the second path being in thesame direction as the flow of finely diffused hydrocarbon through theinjector means, and means for injecting the finely diffused hydrocarboninto the stream of Ysteam flowing through the second path to form agaseous mixture of hydrocarbon and steam.

12. A device according to claim ll including means for mixing additionalsteam with the steam passing from the ilrst path to the second path.

13. A device according to claim 11 including a cracking tube into whichthe injector means extends, spacer means in the cracking tube, means forpassing steam through the spacer means, and means for passing thegaseous mixture of hydrocarbon and steam through the cracking tube.

JAMES H. SHAPLEIGH.

(References on following page) emma REFERENCES CITED The followingreferences are of record in the me of this patent:

UNITED STATES PATENTS f Number Name Date 1,445,040 Read Feb. 13, 19231,477,860 Adams Dec. 18, 1923 1,613,010 Armstrong Jan. 4, 1927 Number

6. A PROCESS OF CRACKING HYDROCARBONS WHICH COMPRISES FLOWINGFINELY-DIFFUSED HYDROCARBON ALONG AN INNER PATH IN A CRACKING TUBE,FLOWING GASEOUS MEDIUM CONCURRENT THEREWITH ALONG AN OUTER PATH IN THECRACKING TUBE AND IN CONTACT WITH THE CRACKING TUBE WALL, APPLYING HEATTO THE CRACKING TUBE, CAUSING THE HYDROCARBON FLOWING FROM THE INNERPATH TO MIX DIRECTLY WITH THE GASEOUS MEDIUM FLOWING ALONG THE OUTERPATH IN CONTACT WITH THE CRACKING TUBE, AND IMMEDIATELY PASSING THEMIXTURE OF GASEOUS MEDIUM AND HYDROCARBON THROUGH THE TUBE WHILEAPPLYING HEAT TO BRING ABOUT SATISFACTORY CRACKING OF THE HYDROCARBONWITHOUT APPRECIABLE CARBON DEPOSITION.
 10. IN A DEVICE FOR THE CRACKINGF HYDROCAR-